The DNR has finalized the most recent updates to the air dispersion modeling guidance. These updates affect the Prevention of Significant Deterioration (PSD) and non-PSD modeling guidelines, the modeling determination form for non-PSD projects (Form MD), the documentation for site-specific background concentrations, and the dispersion modeling checklist. In addition, a new document was created to explain the methodology used to remove the impacts of smoke events from background concentration data.
Seven written comment letters or emails were received during the four-week public comment period, which ended on July 8, 2024. No substantive changes were necessary as a result of the comments, but minor edits were made to the documents, and responses have been sent to the commenters. The final versions of these documents are available on the dispersion modeling webpage, and are effective as of September 1, 2024. There will be a delay before Form MD can be updated in EASY Air. In the interim, applicants may use the new version available on the website and attach it with their application in EASY Air.
Please send any questions to Brad Ashton at Brad.Ashton@dnr.iowa.gov, or by phone at 515-725-9527.